Transparent Bridge Network After STA Is

The spanning-tree calculation occurs when the bridge is powered up and whenever a topology change is detected. The calculation requires communication between the spanning-tree bridges, which is accomplished through configuration messages (sometimes called bridge protocol data units, or BPDUs). Configuration messages contain information identifying the bridge that is presumed to be the root (root identifier) and the distance from the sending bridge to the root bridge (root path cost)....

Apple Talk Enhanced IGRP Clients Cannot Connect to Servers

Symptom Macintosh clients cannot connect to servers in an AppleTalk Enhanced IGRP network environment. Table 9-11 outlines the problems that might cause this symptom and describes solutions to those problems. Table 9-11 AppleTalk Enhanced IGRP Clients Cannot Connect to Servers Table 9-11 AppleTalk Enhanced IGRP Clients Cannot Connect to Servers For information on troubleshooting this problem, see the section AppleTalk Enhanced IGRP Routers Not Establishing Neighbors later in this chapter. For...

Apple Talk Technology Basics

AppleTalk was designed as a client server distributed network system. In other words, users share network resources (such as files and printers) with other users. Computers supplying these network resources are called servers computers using a server's network resources are called clients. Interaction with servers is essentially transparent to the user because the computer itself determines the location of the requested material and accesses it without further information from the user. In...

ATM Label Switching

ATM uses label switching, a technique in which a simple label is placed in the header of each cell. The label provides information used in transporting the cell across the next hop in the network. Networks that do not use label switching usually require each packet (or cell) to contain the explicit address of the final destination. ATM uses label switching because it is simpler, thereby making faster switching possible. 1 A switching unit reads an incoming cell from a particular port. The...

Booting Client ARP Requests Timeout During Netboot

Verify that neighbor routers can ping the server. Use the trace exec command to determine the path to the server. Use the show arp privileged exec command to examine the ARP1 tables or the show ip route privileged exec command to view the IP routing table. Verify that the server is listed and that the routing table entries are appropriate. Use the clear arp-cache and clear ip-route privileged exec commands to force the router to repopulate its ARP and routing tables. Shut down all extra...

Booting Router Hangs After ROM Monitor Initializes

Symptom When a user is booting a Cisco 7000 series, AGS+, AGS, ASM-CS, MGS, IGS, or CGS router from ROM, the system hangs after the ROM monitor initializes. Table 3-19 outlines the problems that might cause this symptom and describes solutions to those problems. Table 3-19 Booting Router Hangs After ROM Monitor Initializes Table 3-19 Booting Router Hangs After ROM Monitor Initializes Inspect EPROM size jumpers. Refer to the hardware installation and maintenance publication for your router to...

Booting Timeouts and Outof Order Packets Prevent Netbooting

Symptom Timeouts or out-of-order packets prevent successful netbooting. The number oftimeouts and out-of-order packets indicated on the router's console display might vary. The following example shows a netbooting session that contains excessive timeouts and out-of-order packets Booting gs3-bfx from 131.108.1.123 O.O .O O OOO.O .O.O The client router might boot in this situation. However, when excessive timeouts and out-of-order packets occur, there is probably a network problem, and netbooting...

Catalyst 1600 Token Ring Switch Startup

When you start up a Catalyst 1600 Token Ring switch, the self-test program automatically checks to see whether the switch is operating correctly. The self-test begins by testing low-level hardware functions and then conducts high-level self-tests. During the high-level self-test, the LCD panel displays the following The version number of the boot software, and the date and time that the software was released The number of each stage in the self-test (these are usually displayed too quickly for...

Catalyst 2900 Series Startup

When you start up a Catalyst 2900 series LAN switch, the following should occur The PS LED on the supervisor engine module faceplate should come on and stay green while power is applied to the system. The system fan assembly and Fan LED should come on and stay on while power is applied to the system. The Status LED on the supervisor engine module and on each interface should be orange until the boot is complete. When the system boot is complete, the supervisor engine module initializes the...

Catalyst 5000 Series Startup

When you start up a Catalyst 5000 series LAN switch, the following should occur The PS1 and PS2 LEDs on the supervisor engine module faceplate should be green. The system fan assembly should be operating and the Fan LED on the supervisor engine module should come on. The Status LED on the supervisor engine module and all interfaces should be orange until the boot is complete. When the system boot is complete, the supervisor engine module should initialize the switching modules. The status LED...

Cip Claw Connection Does Not Come Up

Symptom Common Link Access for Workstations (CLAW) connections do not come up properly over a Channel Interface Processor (CIP). The output of the show extended channel slot port statistics exec command shows N for CLAW connections, indicating that they are down. Table 10-13 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-13 CIP CLAW Connection Does Not Come Up Table 10-13 CIP CLAW Connection Does Not Come Up Step 1 Check whether TCP IP is...

Cisco 7000 Series Startup

When you start up a Cisco 7000 series router, the following should occur The DC OK LED should go on and should remain on as long as the system is receiving source power. The fans should be operating. The Route Processor (RP) Normal LED should go on and stay on to indicate normal system operation the Halt CPU LED should remain off. The Enabled LED on the Switch Processor (SP) or Silicon Switch Processor (SSP) and each interface processor should go on when the RP has completed initialization of...

Cisco 7500 Series Startup

When you start up a Cisco 7500 series router, the following should occur The AC (or DC) OK LED should go on immediately and should remain on as long as the system is receiving power. The blower should be operating. The Route Switch Processor (RSP) and front-panel Normal LEDs should go on (to indicate normal system operation) and should remain on during system operation the CPU Halt LED should remain off. The Enabled LED on each interface processor should go on (to indicate that the RSP has...

Cisco View Timeout Error Messages

Symptom When attempting to use the CiscoView application, you receive timeout messages and cannot view a device. Table 23-7 outlines the problems that might cause this symptom and describes solutions to those problems. Table 23-7 CiscoView Timeout Error Messages Table 23-7 CiscoView Timeout Error Messages Perform the steps outlined in the section Testing Basic Connectivity and Setup earlier in this chapter. Try increasing the polling interval. To increase the polling interval, select Options,...

Cisco Works Sync with Sybase Fails

Symptom Attempts to run Sync with Sybase in CiscoWorks fail. Table 23-2 outlines the problems that might cause this symptom and describes solutions to those problems. Table 23-2 CiscoWorks Sync with Sybase Fails Table 23-2 CiscoWorks Sync with Sybase Fails Follow the steps outlined in the section Testing Basic Connectivity and Setup earlier in this chapter. Run nmadd from the command line to determine whether the problem is related to community string, name resolution, or timing out. The nmadd...

Configuration Management Deviceto Database or Databaseto Device Does Not

Symptom The device-to-database or the database-to-device operation in the Configuration Management application does not work. Table 23-5 outlines the problems that might cause this symptom and describes solutions to those problems. Table 23-5 Configuration Management Device-to-Database or Database-to-Device Does Not Run Table 23-5 Configuration Management Device-to-Database or Database-to-Device Does Not Run Perform the steps outlined in the section Testing Basic Connectivity and Setup Perform...

Configuration Register DIP Switch

Cisco 7000 series running Software Release 9.17(4) or later (Flash netboot) or Cisco IOS Release 10.0 or later (ROM) Cisco 7000 series running Software Release 9.17(4) or later (Flash netboot) or Cisco IOS Release 10.0 or later (ROM) Cisco 7000 running Software Release 9.21 or earlier from ROM Cisco IGS running Software Release 9.1 or later Cisco IGS running software prior to Software Release 9.1

Configuration SnapIn Manager Cannot Modify DoItNow

Symptom The DoItNow operation in the Configuration Snap-In Manager application does not work. Table 23-6 outlines the problems that might cause this symptom and describes solutions to those problems. Table 23-6 Configuration Snap-In Manager Cannot Modify DoItNow Table 23-6 Configuration Snap-In Manager Cannot Modify DoItNow Perform the steps outlined in the section Setup earlier in this chapter. Testing Basic Connectivity and Perform the steps outlined in the section earlier in this chapter....

DECnet Connections to DEC Hosts Fail over Router End Node Problem

Symptom DECnet nodes cannot communicate when attempting to make connections over routers. Note This section focuses on problems in end nodes. For router-related problems and solutions, see the section DECnet Connections to DEC Hosts Fail over Router (Router Problem) later in this chapter. Table 11-1 outlines the problems that might cause this symptom and describes solutions to those problems. Table 11-1 DECnet Connections to DEC Hosts Fail over Router (End Node Problem) Step 1 Check the end...

DECnet Connections to DEC Hosts Fail over Router Router Problem

Symptom DECnet nodes cannot communicate when attempting to make connections over routers. Note This section focuses on problems in the router. For end node-related problems and solutions, see the section DECnet Connections to DEC Hosts Fail over Router (End Node Problem) earlier in this chapter. Table 11-2 outlines the problems that might cause this symptom and describes solutions to those problems. Table 11-2 DECnet Connections to DEC Hosts Fail over Router (Router Problem) Use the show decnet...

DECnet End Nodes Cannot Find Designated Router

Symptom End nodes cannot find a designated router. End nodes cannot access nodes that are on different LANs, but other nodes connected to the same LAN are accessible. Table 11-3 outlines the problems that might cause this symptom and describes solutions to those problems. Table 11-3 DECnet End Nodes Cannot Find Designated Router DECnet not enabled on Step 1 Use the show running-config privileged exec command to view the router router configuration. Determine whether DECnet global configuration...

DECnet No Phase IV Connectivity over Phase V Backbone

Symptom Communication between DECnet Phase IV areas separated by an ISO CLNS (Phase V) backbone fails. Phase IV nodes cannot communicate with other Phase IV nodes across a Phase V cloud. However, nodes can communicate with one another within the same Phase IV cloud. Note For more information about troubleshooting DECnet OSI internetworks, see Chapter 12, Troubleshooting ISO CLNS. Table 11-7 outlines the problems that might cause this symptom and describes solutions to those problems. Table 11-7...

DECnet Router or End Node Sees Incorrect Designated Router

Symptom Routers and end nodes see an incorrect or an unexpected designated router. If your network requires a specific router to be elected the designated router, allowing another router to become a designated router can cause unpredictable network behavior and can block connectivity in and out of the area. Table 11-4 outlines the problems that might cause this symptom and describes solutions to those problems. Table 11-4 DECnet Router or End Node Sees Incorrect Designated Router Priority of...

DECnet Routers Not Establishing Adjacencies

Symptom Routers do not establish adjacencies with other routers on the same LAN. Table 11-5 outlines the problems that might cause this symptom and describes solutions to those problems. Table 11-5 DECnet Router Not Establishing Adjacencies Router area number is higher than configured decnet max-area DECnet limits the number of adjacencies that can be established by a router to 32. Step 1 Enable the debug decnet events privileged exec command to determine whether the adjacency is being...

Descriptions of Environment Variables

The following are descriptions of the CiscoWorks environment variables NMSROOT Default directory for CiscoWorks installation. If the software was installed in a different directory, substitute the appropriate directory path to ensure the correct definition of the NMSROOT environment variable. SYBASE Default directory for Sybase installation. If the software was installed in a different directory, substitute the appropriate directory path to ensure the correct definition of the SYBASE...

Dialin Modem Cannot Send or Receive IP Data

Symptom After a dialin connection is established, a modem cannot send or receive IP data. Note For general problems associated with a modem that cannot send or receive data, refer to the section Dialin Modem Cannot Send or Receive Data earlier in this chapter. Note For information on troubleshooting IP problems not specific to dialin connections, refer to Chapter 7, Troubleshooting TCP IP. Table 16-10 outlines the problems that might cause this symptom and describes solutions to those problems....

Dialin Modem Hangs Up Shortly After Connecting

Symptom A dialin connection is successful but the modem hangs up after 30 to 90 seconds. Table 16-5 outlines the problems that might cause this symptom and describes solutions to those problems. Table 16-5 Dialin Modem Hangs Up Shortly After Connecting Possible Causes Suggested Actions Table 16-5 Dialin Modem Hangs Up Shortly After Connecting Use the show line exec command on the access server or router. The output for the auxiliary port should indicate the currently configured Tx1 and Rx2 For...

Dialin No Connectivity Between Modem and Router

Symptom The connection between a modem and a Cisco access server or router does not work. Attempts to initiate a reverse Telnet session to the modem have no result, or the user receives a connection refused by foreign host message. Note More specific symptoms for dialin connection problems are covered later in this chapter. Table 16-2 outlines the problems that might cause this symptom and describes solutions to those problems. Table 16-2 Dialin No Connectivity Between Modem and Router Possible...

Establishing a Reverse Telnet Session to a Modem

If you are running Cisco IOS Release 11.0 or earlier, you must establish a reverse Telnet session to configure a modem to communicate with a Cisco device. As long as you lock the data terminal equipment (DTE)-side speed of the modem (see Table 16-5 for information on locking the modem speed), the modem will always communicate with the access server or router at the desired speed. Be certain that the speed of the Cisco device is configured prior to issuing commands to the modem via a reverse...

Ethernet and IEEE 8023

Ethernet and IEEE 802.3 specify similar technologies. Both are CSMA CD LANs. Stations on a CSMA CD LAN can access the network at any time. Before sending data, CSMA CD stations listen to the network to see if it is already in use. If it is, the station wishing to transmit waits. If the network is not in use, the station transmits. A collision occurs when two stations listen for network traffic, hear none, and transmit simultaneously. In this case, both transmissions are damaged, and the...

Fault Management Mechanisms

Token Ring networks employ several mechanisms for detecting and compensating for network faults. For example, one station in the Token Ring network is selected to be the active monitor. This station, which can potentially be any station on the network, acts as a centralized source of timing information for other ring stations and performs a variety of ring maintenance functions. One of these functions is the removal of continuously circulating frames from the ring. When a sending device fails,...

Fault Tolerant Features

FDDI provides a number of fault-tolerant features, the most important of which is the dual ring. If a station on the dual ring fails or is powered down or if the cable is damaged, the dual ring is automatically wrapped (doubled back onto itself) into a single ring, as shown in Figure 5-4. In this figure, when Station 3 fails, the dual ring is automatically wrapped in Stations 2 and 4, forming a single ring. Although Station 3 is no longer on the ring, network operation continues for the...

FDDI Specifications

FDDI is defined by four separate specifications (see Figure 5-1) Media Access Control (MAC) Defines how the medium is accessed, including frame format, token handling, addressing, an algorithm for calculating a cyclic redundancy check value, and error recovery mechanisms. Physical Layer Protocol (PHY) Defines data encoding decoding procedures, clocking requirements, framing, and other functions. Physical Layer Medium (PMD) Defines the characteristics of the transmission medium, including the...

Figure 111 DNA and the OSI Reference Model

As Figure 11-1 shows, DNA supports a variety of media and link implementations. Among these are well-known standards such as Ethernet, Token Ring, Fiber Distributed Data Interface (FDDI), IEEE 802.2, and X.25. DNA also offers a traditional point-to-point link-layer protocol called Digital Data Communications Message Protocol (DDCMP) and a 70-Mbps bus used in the VAX cluster called the computer-room interconnect bus (CI bus).

Figure 114 Examples of DECnet Addresses

DECnet hosts do not use manufacturer-assigned Media Access Control (MAC)-layer addresses. Instead, network-level addresses are embedded in the MAC-layer address according to an algorithm that multiplies the area number by 1,024 and adds the node number to the product. The resulting 16-bit decimal address is converted to a hexadecimal number and appended to the address AA00.0400 in byte-swapped order, with the least significant byte first. For example, DECnet address 12.75 becomes 12363 (base...

Figure 152 show controllers cbus Command Output

Switch Processor 5, hardware version 11.1, microcode version 10.7 512 Kbytes of main memory, 128 Kbytes cache memory 4 256 byte buffers, 4 1024 byte buffers, 312 1520 byte buffers 1024 byte system buffer Restarts 0 line down, 0 hung output, 0 controller error FSIP 0, hardware version 1.0, microcode version 175.0 Microcode loaded from system Interface and attached cable information Interface 0 - Serial 0 0, electrical interface is Universal (cable unattached) 22 buffer RX queue threshold, 23...

Figure 155 Extended ping Specification Menu

Datagram size 100 64 specification Extended commands n yes - Extended commands Source address selected option Data pattern OxABCD Oxffff - Data pattern Loose, Strict, Record, Timestamp, Verbose none specification Sweep range of sizes n Type escape sequence to abort. Sending 20, 64-byte ICMP Echos to 12 9.44.12.7, timeout is 2 seconds Packet has data pattern 0xFFFF Success rate is 100 percent, round-trip min avg max 1 3 4 ms In general, perform serial line ping tests as follows Step 1 Put the...

Figure 158 show buffers Command Output

Cookie-Monster> show buffers Buffer elements 401 in free list (500 max allowed) 87777499 hits, 0 misses, 0 created Small buffers, 104 bytes (total 120, permanent 120) 114 in free list (20 min, 250 max allowed) 70005538 hits, 6 misses, 2 trims, 2 created Middle buffers, 600 bytes (total 90, permanent 90) 88 in free list (10 min, 200 max allowed) 25696696 hits, 27 misses, 27 trims, 27 created Big buffers, 1524 bytes (total 90, permanent 90) total identifies the total number of buffers in the...

Figure 172 ISDN Physical Layer Frame Formats

A Activation bit B1 B1 channel bits B2 B2 channel bits D D channel (4 bits x 4000 frames sec 16 kbps) E Echo of previous D bit F Framing bit L Load balancing S Spare bit The frames are 48 bits long, of which 36 bits represent data. The bits of an ISDN physical layer frame are used as follows F Provides synchronization. L Adjusts the average bit value. E Used for contention resolution when several terminals on a passive bus contend for a channel. B1, B2, and D For user data. Multiple ISDN user...

Figure 181 The Frame Relay Frame

Field length, 12 Variable 2 1 Field length, 12 Variable 2 1 The 10-bit DLCI value is the heart of the Frame Relay header. It identifies the logical connection that is multiplexed into the physical channel. In the basic (not extended by the LMI) mode of addressing, DLCIs have local significance that is, the end devices at two different ends of a connection may use a different DLCI to refer to that same connection. Figure 18-2 provides an example of the use of DLCIs in nonextended Frame Relay...

Figure 192 X25 and the OSI Reference Model

End-to-end communication between DTEs is accomplished through a bidirectional association called a virtual circuit. Virtual circuits permit communication between distinct network elements through any number of intermediate nodes without the dedication of portions of the physical medium that characterizes physical circuits. Virtual circuits can be either permanent or switched (temporary). Permanent virtual circuits (PVCs) are typically used for the most often used data transfers, whereas...

Figure 211 User Assignments on Communications Channel Using TDM

Time Time Time Time Time Time Time Time Time Time Time Time slot slot slot slot slot slot slot slot slot slot slot slot The time slots allocated for each user occur at precisely the same time in every frame. Because the time slots are synchronous, TDM is sometimes referred to as synchronous transfer mode (STM). Users can access the communications channel only when a time slot that has been allocated to them is available. For example, User A can send messages over the communications channel only...

Figure 2110 ATM Adaptation Layer Functions

When ATM cells are transferred through a network, each cell is processed in isolation from all other cells. All processing decisions are made based on the cell header no processing of the data in the payload field occurs. Figure 21-11 shows some examples of AAL processing. Figure 21-11 AAL Processing Examples Figure 21-11 AAL Processing Examples Hosts A and C are connected to the network through ATM interfaces, so they do all their AAL processing internally. The network does not do any...

Figure 2112 Information Flow Through AAL

Convergence sublayer (CS) user data is broken up into packets (CS-PDUs) Segmentation and reassembly (SAR) sublayer each CS-PDU is broken up into SAR-PDUs CS-PDU SAR-PDU SAR-PDU To ATM layer CS-PDU SAR-PDU SAR-PDU To ATM layer The convergence sublayer (CS) accepts higher-layer traffic for transmission across the network. Depending on the AAL type, header and or trailer fields are added to the packet. The packet is then segmented by the SAR sublayer to form 48-byte payloads (also known...

Figure 219 The User Network Interface ATM Cell Header Format

Table 21-2 Fields in an ATM Cell Header Table 21-2 Fields in an ATM Cell Header Controls the flow of traffic across the user network interface and thus into the ATM network. Second 4 bits of Byte 1 and the first 4 bits of Byte 2 Identifies a particular VPC3. A VPC is a group of virtual connections carried between two points and may involve several ATM links. VPIs provide a way to bundle traffic heading to the same destination. Second 4 bits of Byte 2, Byte 3, and the first 4 bits of Byte 4...

Figure 95 A Sample Apple Talk ZIT

AURP allows a network administrator to connect two or more AppleTalk internetworks through a foreign network (such as Transmission Control Protocol Internet Protocol TCP IP ) to form an AppleTalk wide-area network (WAN). The connection is called a tunnel, which functions as a single, virtual data link between the AppleTalk internetworks, as shown in Figure 9-6.

Figure B1 show stacks Command Output Showing the Software Program Counter Address

Interrupt level stacks Level Called Free Size 1 306611 952 1000 3 22294573 496 1000 5 2986 968 1000 Multiport Communications Interfaces Console UART System was restarted by error - Software forced crash, PC 0x4854E GS Software (GS3-K), Version 9.1(4) fc1 , SOFTWARE Compiled Thu 25-Mar-93 09 49 by daveu Stack trace from system failure 0x2B0424, 0x2B0458, 0x2B046C, 0X2B04 90, 0x2B04B0, 0x3B04 0xF3 9C2 0xF4566 0x112F0 0x2560 Figure B-2 shows output from a hardware error and includes an example of...

Fitting ATM into the OSI Model

ATM standards define protocols that operate at Layer 2 (the data link layer) of the International Organization for Standardization (ISO) seven-layer Open Systems Interconnection (OSI) reference model. Figure 21-3 shows the layered architecture of the OSI model. The data link layer is concerned with data transmission between two network switches. This layer is not concerned with the transmission of an entire message between a source and a destination switch this responsibility belongs to Layer 3...

Frame Format

FDDI frame formats (shown in Figure 5-7) are similar to those of Token Ring. The fields of an FDDI frame are as follows Preamble Prepares each station for the upcoming frame. Start delimiter Indicates the beginning of the frame. It consists of signaling patterns that differentiate it from the rest of the frame. Frame control Indicates the size of the address fields, whether the frame contains asynchronous or synchronous data, and other control information. Destination address Contains a unicast...

Implementing Hold Queue Limits

Hold queues are buffers used by each router interface to store outgoing or incoming packets. Use the hold-queue interface configuration command to increase the number of data packets queued before the router will drop packets. Increase these queues by small increments (for instance, 25 ) until you no longer see drops in the show interfaces output. The default output hold queue limit is 100 packets. Note The hold-queue command is used for process-switched packets and periodic updates generated...

Input Error Type Field Name

CRC errors occur when the CRC calculation does not pass (indicating that data is corrupted) for one of the following reasons Serial cable is too long or cable from the CSU DSU to the router is not shielded SCTE mode is not enabled on DSU CSU line clock is incorrectly configured Ones density problem on T1 link (incorrect framing or coding specification) Step 1 Ensure that the line is clean enough for transmission requirements. Shield the cable if necessary. Step 2 Make sure the cable is within...

Internet Routing

Routing devices in the Internet have traditionally been called gateways an unfortunate term because elsewhere in the industry, the term gateway applies to a device with somewhat different functionality. Gateways (which we will call routers from this point on) within the Internet are organized hierarchically. Some routers are used to move information through one particular group of networks under the same administrative authority and control (such an entity is called an autonomous system)....

IPX Enhanced IGRP Router Stuck in Active Mode

Symptom An IPX Enhanced IGRP router is stuck in Active mode. The router repeatedly sends error messages similar to the following DUAL-3-SIA Route 3c.0800.0c00.4321 Stuck-in-Active Note Occasional messages of this type are not a cause for concern. This is how an Enhanced IGRP router recovers if it does not receive replies to its queries from all its neighbors. However, if these error messages occur frequently, you should investigate the problem. For a more detailed explanation of Enhanced IGRP...

Ipx Rip Sap Updates Not Propagated by Router

Symptom Novell SAP packets are not forwarded through a router running IPX RIP. Clients might be unable to connect to servers over one or more routers, or they might intermittently be able to connect. Note Procedures for troubleshooting IPX RIP problems not specific to SAPs are described in the section IPX RIP No Connectivity over IPX RIP Router earlier in this chapter. Additional problems relating to intermittent connectivity problems are described in the section Novell IPX Intermittent...

ISDN Components

ISDN components include terminals, terminal adapters (TAs), network-termination devices, line-termination equipment, and exchange-termination equipment. ISDN terminals come in two types. Specialized ISDN terminals are referred to as terminal equipment type 1 (TE1). Non-ISDN terminals such as DTE that predate the ISDN standards are referred to as terminal equipment type 2 (TE2). TE1s connect to the ISDN network through a four-wire, twisted-pair digital link. TE2s connect to the ISDN network...

Iso Clns Host Cannot Access Hosts in Different Area

Symptom Host cannot access hosts in a different area. Hosts in the same area are accessible. Table 12-5 outlines the problems that might cause this symptom and describes solutions to those problems. Table 12-5 ISO CLNS Host Cannot Access Hosts in Different Area Level 2 routers are not routing packets to the correct area ES host is not running ES-IS protocol Step 1 Use the trace command to verify that Level 1 routers are routing packets to the nearest Level 2 router. The following display shows...

Iso Clns Host Cannot Access Hosts in Same Area

Symptom Hosts cannot access other hosts in the same area. The hosts might be on the same network or they might be in a different network in the same area. Table 12-4 outlines the problems that might cause this symptom and describes solutions to those problems. Table 12-4 ISO CLNS Host Cannot Access Hosts in Same Area Area address is configured incorrectly on the host Step 1 Check all Level 1 routing tables and link-state databases. Step 2 Verify that the hosts are in the same area. Step 3 Check...

Iso Clns Host Cannot Access Hosts on Local or Remote Network

Symptom Hosts cannot communicate with other hosts. Hosts might be located on the local or a remote network. Connections to some hosts on a network might be possible, whereas connections to other hosts on the same network fail. Table 12-3 outlines the problems that might cause this symptom and describes solutions to those problems. ISO CLNS Host Cannot Access Hosts on Local or Remote Network Missing or mis-configured default gateway specification Level 1 router or ES has bad address Step 1...

Iso Clns Poor Performance

Symptom Users experience poor performance or sudden loss of connections. One or more routers might be receiving duplicate routing updates and might see routers and ESs on multiple interfaces. Table 12-9 outlines the problems that might cause this symptom and describes solutions to those problems. Table 12-9 ISO CLNS Poor Performance Multiple ISO-IGRP processes are configured on a single interface Bridge or repeater in parallel with router Step 1 Use the show clns interface exec command to view...

Iso Clns Redistribution Causes Routing Problems

Symptom Route redistribution does not work properly and causes routing problems. Traffic does not get through a router that is redistributing routes between two different routing areas or domains typically IS-IS and ISO-IGRP. Observed symptoms range from poor performance to no communication at all. Table 12-8 outlines the problems that might cause this symptom and describes solutions to those problems. Table 12-8 ISO CLNS Redistribution Causes Routing Problems Misordered sequence The sequence...

Media Problem Suggested Actions

Use the show interfaces ethernet exec command to determine the status of the router's Ethernet interfaces. The presence of many CRC errors but not many collisions is an indication of excessive noise. Check cables to determine whether any are damaged. Look for badly spaced taps causing reflections. If you are using 100BaseTX, make sure you are using Category 5 cabling and not another type, such as Category 3. Use the show interfaces ethernet command to check the rate of collisions. The total...

Modem State Modem Hardware State Meaning

Idle CTS noDSR DTR RTS These are the proper modem states for connections between an access server or router and a modem (when there is no incoming call). Output of any other kind generally indicates a problem. Modem State Modem Hardware State Meaning Ready If the modem state is Ready instead of Idle, there are three Modem control is not configured on the access server or router. Configure the access server or router with the modem inout line configuration command. A session exists on the line....

Multicast Open Shortest Path First

Multicast Open Shortest Path First (MOSPF) is an extension to OSPF, which is a unicast routing protocol that requires each router in a network to be aware of all available links in the network. Each OSPF router calculates routes from itself to all possible destinations. MOSPF works by including multicast information in OSPF link states. MOSPF calculates the routes for each source multicast group pair when the router receives traffic for that pair. These routes are cached until a topology change...

Novell SAPs

The list of Novell SAPs in Table 8-14 is unverified information contributed from various sources. Novell, in an official capacity, does not and has not provided any of this information. Table 8-14 Novell SAPs, Their Descriptions, and Their Decimal and Hex Values Table 8-14 Novell SAPs, Their Descriptions, and Their Decimal and Hex Values NACS Async Gateway or Asynchronous Gateway Bridge Server or Asynchronous Bridge Server Point to Point (Eicon) X.25 Bridge Server Time Synchronization Server or...

Novell Technology Basics

As an NOS environment, NetWare specifies the upper five layers of the OSI reference model. It provides file and printer sharing, support for various applications, such as electronic mail transfer and database access, and other services. Like other NOSs, such as the Network File System (NFS) from Sun Microsystems, Inc., and LAN Manager from Microsoft Corporation, NetWare is based on a client server architecture. In such architectures, clients (sometimes called workstations) request certain...

Password Recovery Procedure Cisco 500CS Communication Server

Lost passwords cannot be recovered from Cisco 500-CS communication servers. The only way to recover from a lost password is to return the communication server to its factory default configuration using the reset button located on the top of the case. The following procedure describes how to restore the Cisco 500-CS to its default configuration. Note When you perform this procedure, your configuration will be lost. Step 1 Power down the communication server. Step 2 Press and hold down the reset...

Password Recovery Procedure IGS Running Software Prior to Software Release

Cisco IGS routers have a bank of DIP switches located on the rear panel. These DIP switches are used to set the hardware configuration register and must be used in the password-recovery process if the router is running system software prior to Software Release 9.1. Note If your password is encrypted, you cannot recover it. You must configure a new password. Figure 24-3 shows the password-recovery procedure for the Cisco IGS running software prior to Software Release 9.1. There is another...

Password Recovery Procedure Platforms Running Earlier Software Releases

Cisco CGS, MGS, AGS, and AGS+ platforms, and Cisco 7000 series routers running software prior to Cisco IOS Release 10.0 from ROM, all have their configuration registers in the hardware, so you must physically change the position of the configuration register jumper during the password-recovery process. It might be necessary to remove the processor card from the router chassis in order to access the hardware configuration register jumper. Consult your hardware documentation for detailed...

Password Recovery Procedure Platforms Running Recent Software Releases

The Cisco CGS, MGS, AGS, and AGS+ platforms, and Cisco 7000 series routers running software prior to Cisco IOS Release 10.0 from ROM, all have their configuration registers in hardware, so you must physically change the position of the configuration register jumper during the password-recovery process. It might be necessary to remove the processor card from the router chassis in order to access the hardware configuration register jumper. Consult your hardware documentation for detailed...

Physical Connections

IEEE 802.3 specifies several different physical layers, whereas Ethernet defines only one. Each IEEE 802.3 physical layer protocol has a name that summarizes its characteristics. The coded components of an IEEE 802.3 physical-layer name are shown in Figure 4-1. Figure 4-1 IEEE 802.3 Physical Layer Name Components Figure 4-1 IEEE 802.3 Physical Layer Name Components A summary of Ethernet Version 2 and IEEE 802.3 characteristics appears in Table 4-1. Table 4-1 Ethernet Version 2 and IEEE 802.3...

Possible Causes Suggested Actions

Check to see whether the answering modem has MNP5 error If MNP5 is enabled on the answering modem, disable it. For information on checking or changing the modem configuration, refer to the modem documentation. Use the show appletalk route and show appletalk zones privileged exec commands to determine whether the router can see its ARA routes and zones. Use the show appletalk interface ethernet exec command and make sure that the output matches your Apple network parameters. Change the interface...

Possible Problem

Step 1 Check to see whether the fan is operating. If it is not, check the fan or the 12 V power supply. Step 2 If the system shuts down after being on for a short time, check the power supply. Step 3 If the power supply appears operational, the router might have shut down due to overheating. Ensure that the chassis intake and exhaust vents are clear. Step 4 If the system does not boot up but the System OK LED is on, check the 12 V power supply to make sure it is not faulty. Step 5 If the system...

Possible Problem Area

Step 1 Check to see whether the RP1 LEDs come on when system power is turned on. Step 2 If none of the RP LEDs come on, make sure that both the fan and power supply are functioning properly. Step 3 If the power supply and fans appear operational but none of the RP LEDs are on, an improperly connected RP, SP2 (or SSP3), or interface processor might have hung the bus. Step 4 If the SP (or SSP) Enabled LED is off but any of the RP LEDs are on, make sure the SP (or SSP) is seated in its slot...

Possible Problem Solution

Use the show running-config privileged exec command to view the router configuration. Check for the ip default-gateway global configuration command, ip-address IP address of the router. If the command is missing, add it to the configuration. If the command is present, make sure it specifies the correct IP address. Step 1 Use the show running-config privileged exec command to view the router configuration. Check the boot server address (IP address of a TFTP server or MAC1 address of a MOP2...

Possible Problems

Misconfigured access lists or other filters Step 1 Use the show appletalk globals exec command to determine whether the internetwork is in compatibility mode. Step 2 Enable the appletalk name-lookup-interval global configuration command and use the show appletalk neighbors exec command to determine which specific neighbor (by NBP1 name) is in compatibility mode. Step 3 To resolve the problem, you can perform one of the following actions Upgrade AppleTalk Phase 1 routers to AppleTalk Phase 2 and...

Possible Problems Solution

Active timer value is The active timer determines the maximum period of time that an Enhanced IGRP router misconfigured will wait for replies to its queries. If the active timer value is set too low, there might not be enough time for all the neighboring routers to send their replies to the Active router. Step 1 Check the configuration of each Enhanced IGRP router using the show running-config privileged exec command. Look for the timers active-time router configuration command entry associated...

Preventive Action

When you change a router or interface configuration, enable the debug apple error privileged exec command to log errors Design your network with attention to the direction in which traffic will flow and minimize the number of different zones in the internetwork The debug apple error privileged exec command tracks the progress and status of changes in the internetwork and alerts you to any errors. You can also run this command periodically when you suspect network problems. In a stable network,...

Protocol Independent Multicast

Multicast traffic tends to fall into one of two categories traffic that is intended for almost all LANs (known as dense) and traffic that is intended for relatively few LANs (known as sparse). Protocol Independent Multicast (PIM) is an Internet draft (under discussion by the IETF Multicast Routing Working Group) that has two modes of behavior for the two traffic types dense mode (DM) and sparse mode (SM). A router that is running PIM can use dense mode from some multicast groups and sparse mode...

Recovering a Lost Password

This section describes the procedures required to recover a lost login or enable password. The procedures differs depending on the platform and the software used, but in all cases, password recovery requires that the router be taken out of operation and powered down. If you need to perform one of the following procedures, make certain that secondary systems can temporarily serve the functions of the router undergoing the procedure. If this is not possible, advise all potential users and, if...

Ripigrp Routes Missing from Routing Table

Symptom Routes are missing from the routing table. Hosts on one network cannot access hosts on a different network. Error messages stating host or destination unreachable are generated. The problem might be occurring in an internetwork running only RIP or IGRP, or a combination of the two. Table 7-9 outlines the problems that might cause this symptom and describes solutions to those problems. Table 7-9 RIP IGRP Routes Missing from Routing Table Misconfigured or Step 1 Use the show...

RSRB Host Cannot Connect to Server Peers Open

Symptom Hosts cannot make connections to servers across a router configured as an RSRB. The output of the show source-bridge privileged exec command shows that SRB peers are open. The following is an example of output from the show source-bridge command Peers state lv pkts_rx pkts_tx expl_gn drops TCP TCP 150.136.93.93 open 2* 18 18 3 0 0 Table 10-4 outlines the problems that might cause this symptom and describes solutions to those problems. Table 10-4 RSRB Host Cannot Connect to Server (Peers...

SDLC Sessions Fail over Router Running STUN

Symptom SDLC sessions between two nodes fail when they are attempted over a router that is running serial tunnel (STUN). Note This section discusses troubleshooting procedures for STUN without local acknowledgment (LACK). For STUN with LACK, the procedures are essentially the same, but remember that there are two sessions, one from the primary to the router, and one from the secondary to the router. Table 10-12 outlines the problems that might cause this symptom and describes solutions to those...

Show interfaces ethernet Field Descriptions

Ethernet is up is administratively down Indicates whether the interface hardware is currently active and whether it has been taken down by an administrator. Disabled indicates that the router has received more than 5,000 errors in a keepalive interval, which is 10 seconds by default. is up down administratively down Indicates whether the software processes that handle the line protocol believe the interface is usable (that is, whether keepalives are successful) or if it has been taken down by...

Show stacks Command Output Showing the Hardware Address

Minimum process stacks Free Size Name 970 1000 env delay init 866 1000 Router Init 554 1000 Init 1500 2000 Exec Interrupt level stacks Level Called Free Size 1 16803 956 1000 env-flash cBus Interfaces Console UART System was restarted by bus error at PC 0x71EAE, address 0x210C008 GS Software (GS3-K), Version 9.1(5), RELEASE SOFTWARE Compiled Wed 19-May-93 18 35 by daveu Stack trace from system failure Hardware address in the bus controller address space

Split Horizon Example

Sometimes in a multipoint WAN environment it is desirable to leave split horizon disabled. However, steps should be taken to prevent routing information from being learned from the wrong interface or protocol. For example, in the environment shown in Figure 7-11, Router 2 might incorrectly receive information about RIP networks from Router 3 if the routers are not configured correctly. Figure 7-11 A Split Horizon Sample Network Figure 7-11 A Split Horizon Sample Network RIP routing information...

SRB Algorithm

SRBs are so named because they assume that the complete source-to-destination route is placed in all inter-LAN frames sent by the source. SRBs store and forward the frames as indicated by the route appearing in the appropriate frame field. Figure 10-3 illustrates a sample SRB network.

Suggested Actions

Attempt to access exec mode by issuing a carriage return. Line is configured with the no exec command Step 1 Use the show line exec command to view the status of the appropriate line. Check the Capabilities field to see whether it says exec suppressed. If this is the case, the no exec line configuration command is enabled. Step 2 Configure the exec line configuration command on the line to allow exec sessions to be initiated. This command has no arguments or keywords. The following example...

Table 1012 SDLC Sessions Fail over Router Running STUN

Step 1 Use the show stun exec command to see whether the peers are open. Ifthe peers are open, one of the other problems in this table is probably the cause. The following is sample output from the show stun command Router show stun This peer 131.108.10.1 Serial0 -- 3174 Controller for test lab (group 1 sdlc ) state rx-pkts tx-pkts drops poll 7 1 IF Serial1 open 20334 86440 5 8P 10 1 TCP 131.108.8.1 open 6771 7331 0 all 1 TCP 131.108.8.1 open 612301 2338550 1005 In this display, the first entry...

Table 1018 CIP Host Running Routed Has No Routes

RIP not properly configured on the router Step 1 Use the show running-config privileged exec command to view the router configuration. Make sure RIP is configured on the router. If RIP is not configured, configure it. Step 2 Check the configuration to see whether there are network statements for each of the networks that should be advertised in RIP updates. If they are missing, add them to the configuration. Step 3 Make sure the passive-interface command is not configured on the channel...

Table 152 Serial Lines Increasing Output Drops on Serial Link

Input rate to serial interface exceeds bandwidth available on serial link Minimize periodic broadcast traffic such as routing and SAP1 updates by using access lists or by other means. For example, to increase the delay between SAP updates, use the ipx sap-interval interface configuration command. Increase the output hold queue size in small increments (for instance, 25 percent), using the hold-queue out interface configuration command. On affected interfaces, turn off fast switching for heavily...

Table 169 Dialin Modem Cannot Send or Receive Data

Possible Causes Suggested Actions Modem speed setting is not locked Step 1 Use the show line exec command on the access server or router. The output for the auxiliary port should indicate the currently configured Tx and Rx speeds. For an explanation of the output of the show line command, see the Using debug Commands section earlier in this chapter. Step 2 If the line is not configured to the correct speed, use the speed line configuration command to set the line speed on the access server or...

Table 176 ISDN Second B Channel Does Not Come Up

Missing or misconfigured dialer load-threshold Step 1 Use the show running-config privileged exec command to view the router configuration. Check for a dialer load-threshold interface configuration command entry. The following is the syntax for the dialer load-threshold command dialer load-threshold load outbound inbound either This command defines the load level that must be exceeded on the first ISDN B channel before the router attempts to bring up a second B channel for a multilink PPP...

Table 201 Transparent Bridging No Connectivity

Step 1 Use the show bridge exec command to see whether there is a connectivity problem. If there is, the output will not show any MAC1 addresses in the bridging table. Step 2 Use the show interfaces exec command to determine whether the interface and line protocol are up. Step 3 If the interface is down, troubleshoot the hardware or the media. Refer to Chapter 3, Troubleshooting Hardware and Booting Problems. Step 4 If the line protocol is down, check the physical connection between the...

Table 2410 Xtacacs Users Cannot Connect Using Xtacacs

Missing login tacacs command Step 1 Use the show running-config privileged exec command on the router to see whether the login tacacs line configuration command is present. Step 2 If the command is not present, add the command on each line that should use XTACACS. For example, to configure line 2 to use XTACACS, enter the following commands C2500(config) line 2 C2500(config-line) login tacacs For detailed information on configuring XTACACS, refer to the Cisco IOS Configuration Fundamentals...

Table 248 Xtacacs Daemon Not Up and Running

Launch the XTACACS daemon with the command xtacacsd -s -l. Step 1 Check the etc services file for the following line Step 2 This line must be included in the file. If the line is not present, add the line Check the directory where you installed xtacacsd for the xtacacsd file. If the executable is not present, use the make command to compile xtacacsd.

Table 718 HSRP Hosts Cannot Reach Remote Networks

Default gateway is not specified or is incorrectly specified on local or remote hosts Step 1 Determine whether local and remote hosts have a default gateway specification. Use the following UNIX command Check the output of this command for a default gateway specification. Step 2 In a network running HSRP, hosts must use the hot standby IP address as their default gateway specification. Use the show standby privileged exec command to check the current hot standby IP address. Step 3 You can...

Table 813 Novell IPX Slow Performance

Novell servers not processing SAP updates as quickly as router is generating them Step 1 Use the show interfaces privileged exec command to check for output drops. Step 2 If there are excessive drops, use the show ipx servers exec command on the router. Compare the output of this command with the output of the display servers system console command on Novell servers. Step 3 If the display servers output for a Novell server shows only a partial listing of the SAP entries shown by the router, the...

Table 87Ipx Rip Sap Updates Not Propagated by Router

Use the show running-config privileged exec command to view the router configuration. Look for ipx sap-interval interface configuration In the following example, SAP updates are sent (and expected) on serial On LAN interfaces, it is recommended that you use the default SAP interval of one minute because the interval on servers cannot be changed. To restore the default value, use the no ipx sap-interval command. The following is the syntax for the ipx sap-interval command minutes Interval, in...

Tacacs Cannot Compile Daemon

Symptom Attempts to compile the TACACS+ daemon result in errors. Table 24-2 outlines the problems that might cause this symptom and describes solutions to those problems. Table 24-2 outlines the problems that might cause this symptom and describes solutions to those problems. make is not in PATH or is not installed on the UNIX machine Enter the command which make at the UNIX prompt. If the output says No make in PATH , make is not in the specified path or is not installed. If make is already...

Tacacs Daemon Not Up and Running

Symptom The TACACS+ daemon is not running. Table 24-3 outlines the problems that might cause this symptom and describes solutions to those problems. Table 24-3 TACACS+ Daemon Not Up and Running Table 24-3 TACACS+ Daemon Not Up and Running Launch TACACS+ with the command tac_plus -C configuration filename. Step 1 Check the etc services file for the following line Step 2 This line must be included in the file. If the line is not present, add the line tac_plus executable does not The TACACS+...